Giovani was substituted at half-time having set-up Mexico's equaliser in the 31st minute against Japan at Wembley.
The forward swung in a corner that was headed home by Marco Fabien.
That made it 1-1 at the break and goals from Oribe Peralta and Javier Cortez secured Mexico's place in the showpiece event on Saturday.
Sandro played the full 90 minutes as Brazil cruised to a 3-0 victory against South Korea at Old Trafford.
The midfielder played his part in the first goal, winning possession on half-way and setting-up the move that ended with Romulo slotting home at the near post.
Two quickfire goals from Leandro Damiao in the 57th and 64th minutes saw Brazil home as they aim for their first Olympic title.